Method for disassembling a spray drying system

ABSTRACT

The present invention relates to a spray drying system provided with a neutralizing system, which system is intended for use in the pharmaceutical industry or in other industries, where the product is e.g. infectious, toxic or highly reactive and constitutes a risk for the surroundings and/or a health risk to people handling the product. The spray drying system comprises a spray drying chamber ( 1 ) comprising a drying chamber ( 1 ) provided with an atomizer device ( 17 ), followed by units ( 2, 3 ) for collecting of product powder and means ( 8 ) for cleaning the exhaust gas, wherein an atomization device ( 16 ) connected to a vessel ( 13 ) containing a neutralizer agent is placed upstream of the drying chamber ( 1 ). The invention also relates to a method which method comprises the following steps: i) sterilizing the spray drying system if the process has to be conducted under aseptic conditions, ii) processing by drying a fluid feed added to a drying chamber ( 1 ) through one or more atomization nozzle(s) ( 16 ), iii) neutralizing comprising adding a neutralizing agent upstream of the drying chamber ( 1 ), iv) cleaning the spray drying system.

The present invention relates to a spray drying system provided with a neutralizing system, which system is intended for use in the pharmaceutical industry or in other industries, where the product is e.g. infectious, toxic or highly reactive and constitutes a risk for the surroundings and/or a health risk to people handling the product.

Spray drying has been applied to many applications within Pharmaceutical and Chemical areas. New applications are arising with special requirements. One new spray drying application is the processing of biological substances and potent compounds such as pharmaceuticals which could be toxic in small amounts. These biological substances and potent compounds require novel and different processing technology than traditional spray drying applications.

A spray drying system for a pharmaceutical process is normally of a size where the expected range of process gas flow rate is between 15-15000 kg/hr.

Traditional spray dryers have four basic components: one or more atomizer units, a unit for providing hot gas, a drying chamber and a particle recovery system. The four basic stages of a spray drying process therefore comprise:

-   -   1. Atomization: A liquid feed stock is atomized into droplets         via either a nozzle or a rotary atomizer. Nozzles use pressure         or compressed gas to atomize the feed while a rotary atomizer         uses a wheel rotating at high speed.     -   2. Drying: Heated process gas (normally air or nitrogen) is         brought into contact with the atomized feed using a gas         disperser—leading to evaporation.     -   3. Particle formation: As the liquid rapidly evaporates from the         droplet, a particle forms and falls to the bottom of the         chamber.     -   4. Recovery: The powder is recovered from the exhaust gases         using a cyclone or bag filter.

The whole spray drying process generally has a short processing time in the order of a few seconds or on special circumstances a longer time. Spray drying can take place in a single stage or in a multistage dryer.

INVENTION

Processing a biological or potent compound in a spray dryer requires containment i.e. the material inside the spray drying system should not be allowed to get in contact with the environment or people working with the spray drying system.

A traditional way to avoid contact with the surroundings is to use glove box isolators. These isolators are sealed units with a conditioned air system. To manipulate the processor within the unit the operator accesses the enclosure through gloved hands. Items required to be used or removed during processing are accessed through rapid transport ports.

If an infectious substance or potent compounds are processed the processor will be contaminated after the processing is complete and the spray drying system has to be thoroughly cleaned before the next batch.

Small spray drying systems are normally disassembled and washed.

Larger spray drying systems can use nozzles that are inserted for cleaning in place. To clean these larger systems operators have to remove the atomization nozzle and replace it with a cleaning technology. This cleaning technology may be a static spray ball or a mechanically rotating spray nozzle. The nozzles have to be inserted into ductwork or vessels by removing either plugs or other equipment i.e. atomization nozzle.

Before cleaning both the smaller and the larger systems it is therefore necessary to open the system which put the operators and the surroundings at risk of being exposed to the processed substances.

Therefore the spray drying system should in order to reduce or preferably remove the risk to operators and surroundings be prepared for opening by neutralizing or deactivating the fine powder inside the equipment before the surroundings are exposed to the content of the spray drying system. The deactivation system preferably control fugitive dusts by wetting them.

SUMMARY OF THE INVENTION

The present invention relates to a method for processing hazardous substances in a spray drying system. The method comprises the following steps:

i) sterilizing the cleaned spray drying system, this process step is optionally and is only needed if the process has to take place under aseptic conditions, ii) processing a feedstock, iii) neutralizing by adding a neutralizing agent to the system upstream of the atomization nozzle and iv) cleaning the spray drying system.

According to one embodiment of the method the neutralizing step comprises wetting the inner surfaces of the spray drying system with a neutralizing aerosol. The aerosol normally has a mean droplet diameter between 0.1-50 μm.

According to a second embodiment of the method the neutralizing step comprises adding a gas to the system.

According to one embodiment of the method the neutralizing step comprises dedusting, disinfecting or chemically neutralizing.

According to one embodiment of the method the neutralizing agent in step iii) is added while drying gas flows at normal design rates i.e. rates and amounts normally used during the drying process.

The present invention relates to a spray drying system for processing toxic, highly reactive or contaminating substances which system comprises a spray drying chamber comprising a drying chamber provided with an atomizer device, followed by units for collecting of product powder and means for cleaning the exhaust gas where an atomization device connected to a vessel containing a neutralizer agent is placed before i.e. upstream of the drying chamber.

According to one embodiment of the system the atomization device is placed on the gas inlet for drying gas to the drying chamber (1) after one or more filters filtering the process gas i.e. the atomization device is placed between the filter(s) and the drying chamber.

According to one embodiment of the system the atomization device (16) is a two fluid nozzle, a single fluid nozzle or a venture.

According to one embodiment of the system the atomizer nozzle is connected to a tank containing neutralizing agent.

According to one embodiment of the system comprises a drying chamber, after treatment equipment placed downstream of the drying chamber and a process gas heater placed upstream in relation to the drying chamber, where an inlet filter capable of removing microorganisms at a temperature below 140° C., is placed upstream of the process gas heater and that the process gas heater is a non-flaking heater.

DETAILED DESCRIPTION OF THE INVENTION

The invention is illustrated in the drawings where:

FIG. 1 shows a spray drying system provided with a nozzle for atomizing neutralizing agent and a by-pass system.

FIG. 2 shows a spray drying system provided with a gas neutralizing system.

FIG. 3 illustrates the locations of deactivation affected by front nozzle(s).

FIG. 4 illustrates the locations of deactivation by atomization nozzle(s).

The spray drying system according to the present invention is designed for biologic or hazardous compound processing. The deactivation system of the spray drying system will disinfect, deactivate, neutralize and/or de-dust the internal product contact surfaces of the spray drying system as a preparation for a thorough chemical cleaning inside and/or outside the containment isolator or bio-safety cabinet.

The sanitization system wets the processor surfaces by creating a fog or aerosol, i.e. a suspension of liquid particles in a carrier gas, comprising a neutralizing agent such as a disinfectant or deactivation agent or an agent for dedusting. The sanitization systems will not clean the spray drying system of contaminates, it will only neutralize the compounds which have been processed in the spray drying system by e.g. disinfecting, deactivating or de-dusting. The choice of and actual effectiveness of the neutralizing agent should be determined based on the biological or chemical characteristics of the solution. It should also be considered if the spray drying system itself put restrictions on which agents can be used e.g. disinfectants or deactivation agents containing disinfecting chlorinated compounds may damage stainless steel surfaces.

The spray drying system according to the invention requires the addition of an atomization device in front i.e. upstream of the drying chamber (see FIGS. 1 and 2) to create the aerosol and thereby to disinfect, deactivate or provide dust control of internal surfaces in the spray dryer system, especially the inner surfaces of the drying chamber. The atomization device in the spray drying system providing the treatment can be a two fluid nozzle, a single fluid nozzle, a venture or another atomizing device. This atomization device will treat the front “clean” side of the drying system plus aid in treating down stream components. Treatment occurs while the process i.e. the drying gas flow at normal design rates.

During the processor treatment the product atomization nozzle i.e. the nozzle(s) through which the liquid feed stock enters during processing can also provide atomization of the treatment agent. The product atomization device will participate in treatment of equipment down stream of the nozzle.

The treatment agent can blind the exhaust filter during wetting. Therefore the treatment system may require a by pass around the exhaust filter. The bypass can include a demister devise and an exhaust filter.

A spray drying system converts both aqueous and non aqueous solutions and suspensions into free flowing powders. The system will normally use heated filtered nitrogen or air as a drying gas.

FIG. 1 shows a spray drying system according to the invention which system comprises a drying chamber 1, a cyclone 2 separating the powder product from the hot process air and a product container 3 in which the dry powder product is collected. The feed liquid is transferred from a feed tank 15 to a mixing chamber 18 by a pump 11. In the mixing chamber 18 the feed is mixed with a gas which gas is heated in an atomization gas heater 7 and afterwards filtered in a filter 6 thereby removing unwanted impurities from the gas. The atomization gas is normally nitrogen or air which might have been sterilized. The feed/gas mixture enters into an atomization nozzle lance mounted in a gas disperser at the top of the drying chamber 1.

The feed will be sprayed through one or more atomization nozzles 17 into the drying chamber 1, where it will be mixed with hot drying or process gas which hot drying gas has been heated in the heater 5 and afterwards filtered in the filter 4. In the drying chamber 1 the feed comes in contact with the heated drying gas this causes the liquid feed fraction to vaporize and the non-volatile portion of the feed forms solid particles.

The vapors and dry particles will be conveyed thru an outlet duct to the high efficiency cyclone 2. The dried particles are removed from the process gas in the cyclone 2 and the process gas exits the cyclone 2 and passes through an exhaust filter 8 placed in connection with the outlet of the cyclone 2. Afterwards the exhaust gas can pass thru a not shown police filter before entering a vent system.

The product collection containers 3 will also be changed inside the containment area. The area where the product collection containers 3 are changed should be isolated from the operating environment.

At the completion of the spray dryer product run, the product container 3 has to be isolated. The operator can manually switch the feed line to water which causes water or another cooling/cleaning fluid to flow from a tank 14 to the drying chamber 1 via the pump 11. The inlet temperature of the drying chamber 1 is lowered as the water feed flows to the atomization nozzle 17. The water evaporates and thereby cools the drying chamber and other down stream equipment. When the temperature of the drying chamber 1 reaches 15-60° C. the cooling fluid is turned off and the spray drying system can be further cooled by passing unheated drying gas thru the system until the chamber outlet reaches ambient temperature.

When the drying chamber 1 outlet has reached ambient temperature the feed is switched to the deactivation agent where after fluid is transferred from a tank 13 containing the deactivation agent to the drying chamber. The deactivation agent enters the drying chamber 1 either by the feed line by the pump 11 or by the process gas line by a pump 12 or by both connections. When entering the drying chamber 1 by the process gas line the liquid deactivation agent enters the gas flow in the line for the process gas as an aerosol or a fog via one or more fogging nozzles 16. The fogging nozzle 16 can be fed by a peristaltic pump 12.

The compressed gas in the process gas connection and gas/liquid suspension exiting the atomization nozzle will spray disinfectant liquid into the drying chamber 1 and all other down stream equipment. All surfaces throughout the spray drying system shall be wetted with agent and this is achieved by controlling the flow of deactivation agent i.e. the amount of incoming deactivation agent, and the time the deactivation agent is added to the equipment. The agent fogging nozzle should only be turned on if the exhaust filter 8 is in the process gas path.

The source gas pressure should be monitored. If the process gas outlet pressure rises this can indicate that the exhaust filter 8 has become wet and should be isolated and bypassed. The valves around the exhaust filter 8 will switch state and send the exhaust process gas through a mist eliminator or liquid trap 9 which mist eliminator 9 removes liquid droplets and then the exhaust process gas enters into an exit filter 10 before entering the vent system.

The deactivation process should be continued until all internal surfaces of the spray drying system are wet. Then all gas and liquid flow should be discontinued and the spray drying system isolated. If necessary the spray drying system could be held until the deactivation agent has neutralized the system surfaces. In the case of deposits only the wetted surfaces will be neutralized or stabilized. The outside surface shall be wetted with disinfected or deactivation agent.

The following agents are example of Chemical/disinfectant Agents which can be used in connection with the deactivation process according to the invention:

Chlorine bleach (sodium Hypochlorite)

Halogens (Chlorines, Alcide) Iodophors

Mulitcycles Providone Iodine chlorhexidine

Alcohols (Acidified) Phenols Cresols (Centra, Cides 7, Oanicide, CidexPlus)

-   -   Sporocidin Banicide     -   Glutaqrex     -   Sterile Biocide     -   Wavicide 01     -   Wavicide 06     -   Synthetics and chlorophenols     -   Bitaphene     -   Expose     -   Matar     -   Beaucoup         Synergistic dual phenolics     -   Pathex

Omni II Multicide Baliant One Stoke Environ Vestal LpH Wexide Sufactants

-   -   Quaternary     -   Amoniums

Dyes Chloroquanidines

Combination Chloroquanidines with Sulfas

Renalin Acids Caustics CIP 100 CIP 200 CIP 300

Other cleaning solutions

FIG. 2 shows an alternative system which is not using liquid deactivation/disinfectant agents, the spray drying system shown in FIG. 2 uses deactivation/disinfectant agents in gas form. This spray drying system will not provide dust control. According to this system a gas deactivation/disinfectant agent is drawn into the spray drying system after the drying process has been ended by using an inductor or another vacuum producing device 18. The vacuum producing device 18 is turned on at the conclusion of the drying process after the powder product has been confined in the product containers 3 when the vacuum producing device 18 is turned on deactivation/disinfectant agent is drawn into the drying chamber 1 via the valve 16 placed in the process gas connection. As the deactivation/disinfectant agent is in gas form it will not cause any wetting of the internal surfaces of the spray drying system. The deactivating gas should be held in the spray drying system until the deactivating action has been completed. This gas introduction could be part of VHP (Vapor phase hydrogen peroxide) sterilization or sanitization for the enclosure.

The gas deactivation/disinfectant system includes a place for a deactivating/disinfecting gas to enter the system and a device will either draw the deactivating/disinfecting gas into the spray drying system or push the gas into the spray drying system. This is normally a part of a treatment to disinfect the processing environment around the spray drying system, the internals of the containment enclosure. When the gas disinfectant is used to treat the enclosure it will be drawn into the processor to treat the processor.

The device to create vacuum could be a liquid or gas eductor, a venture, a vacuum pump, a mechanical compressor or a steam jet. The disinfectant gas could be pushed into the system using a centripetal fan, positive displacement blower compressor or other flow producing device.

FIG. 3 shows the system of FIG. 1 where the zone exclusively affected by deactivation agent being added through the fogging nozzles 16 is marked. This zone covers the “upstream” parts of the drying chamber i.e. those parts which liquid flowing from the atomization does reach.

FIG. 4 shows the system of FIG. 1 where the zone affected by deactivation agent being added through the atomization nozzles 17 is marked. This zone covers the “downstream” parts of the drying chamber, cyclone i.e. those parts which liquid flowing from the atomization does reach. This zone would also be affected by deactivation agent being added through the fogging nozzles 16 alone but if deactivation agent is only added through the fogging nozzles 16 that would mean that the neutralizing step would take longer time compared to a situation where both the fogging and the atomization nozzles are used in the neutralizing step. 

1. Method for processing hazardous substances in a spray drying system, wherein the method comprises the following steps: i) sterilizing the spray drying system if the process has to be conducted under aseptic conditions, ii) processing by drying a fluid feed added to a drying chamber through one or more atomization nozzle(s), iii) neutralizing comprising adding a neutralizing agent upstream of the drying chamber, iv) cleaning the spray drying system.
 2. Method according to claim 1, wherein the neutralizing step iii) comprises wetting the inner surfaces of the spray drying system with a neutralizing aerosol.
 3. Method according to claim 1, wherein the neutralizing step iii) comprises dedusting, disinfecting or chemically neutralizing.
 4. Method according to claim 2, wherein the neutralizing aerosol has a mean droplet diameter between 0.1-50 μm.
 5. Method according to claim 1, wherein the neutralizing agent in step iii) is added while drying gas flows at normal design rates.
 6. Spray drying system for processing toxic, highly reactive or contaminating substances, wherein said system comprises a spray drying chamber provided with an atomizer device, followed by units for collecting of product powder and means for cleaning the exhaust gas, and wherein an atomization device connected to a vessel containing a neutralizer agent is placed upstream of the drying chamber.
 7. Spray drying system for processing hazardous substances according to claim 6, wherein the atomization device is located at the gas inlet for drying gas to the drying chamber after one or more filters filtering the process gas.
 8. Spray drying system for processing hazardous substances according to claim 6, wherein the atomization device is one of the following: a two fluid nozzle, a single fluid nozzle or a venture.
 9. Spray drying system for processing hazardous substances according to claim 6, wherein the atomizer nozzle is connected to a tank containing neutralizing agent.
 10. Spray drying system for processing hazardous substances, wherein said system comprises a drying chamber, after treatment equipment placed downstream of the drying chamber and a process gas heater placed upstream in relation to the drying chamber, wherein an inlet filter capable of removing microorganisms at a temperature below 140° C., is placed upstream of the process gas heater, and wherein the process gas heater is a non-flaking heater.
 11. Spray drying system for processing hazardous substances according to claim 10, wherein the atomizer nozzle is connected to a tank containing neutralizing agent.
 12. Spray drying system for processing hazardous substances according to claim 10, wherein an atomization device is located upstream of the drying chamber, which atomization device is connected to a vessel containing a neutralizer agent.
 13. Spray drying system for processing hazardous substances according to claim 12, wherein the atomization device is located at the gas inlet for drying gas to the drying chamber.
 14. Spray drying system for processing hazardous substances according to claim 13, wherein the atomization device is located downstream of one or more filters filtering the process gas.
 15. Spray drying system for processing hazardous substances according to claim 12, wherein the atomization device is one of the following: a two fluid nozzle, a single fluid nozzle or a venture. 